The present invention relates to a digital copier of the type writing image data read by a scanner in a memory and transferring them from the memory to a printer.
It is a common practice with a digital copier of the type described to write image data representative of a single document and read by a scanner in a memory capable of accommodating one or more pages. The image data are transferred from the memory to a printer to be printed out. This type of copier can form a plurality of images repeatedly only if a document is read once and, therefore, has inherently high copying speed. In addition, when a plurality of documents should be reproduced, it is possible to cause, before the reproduction of the preceding document ends, the copier to sequentially read the following documents, store the resulting image data in the memory, and waits until the reproduction of the preceding document ends.
However, the problem with the conventional digital copier described above is that the capacity of the memory and, therefore, the number of documents which can be sequentially read is limited. Moreover, the document size sometimes exceeds the capacity of the memory. Hence, when the amount of image data exceeds the upper limit of the memory capacity, image data are inhibited from being written to the memory, or image data stored in the memory are destroyed. When image data in the memory are destroyed, the operator has to cause the scanner to read the documents all over again or otherwise deal with such an occurrence.